Pattern projection is known as a non-contact method of measuring the 3D shape of an object surface (for example, patent literature (PTL) 1 and PTL 2). With this method, a specific standard pattern is first projected onto an object to be measured. The projected pattern, which deforms in accordance with the 3D shape of the surface on which the pattern is projected, is then captured with an imager from a different direction than the projection direction, and the imaged pattern is analyzed to calculate the 3D shape of the surface to be measured.
For example, PTL 1 discloses a measurement apparatus disposed at the tip of an endoscope. The phase shift method is used in this apparatus to measure the 3D shape of the surface of the object to be measured. With the phase shift method, an interference fringe is projected onto the object to be measured, the phase of a projected grid pattern is sequentially changed, and on the basis of captured image data, the initial phase distribution is calculated. The shape of the object surface can be calculated in accordance with this phase distribution by the principle of triangulation.
Such a measurement method based on pattern projection offers advantages such as not damaging the object for measurement by being a non-contact method, allowing measurement of soft objects, allowing rapid measurement and measurement of dynamically changing objects by virtue of instantaneously obtaining information over a wide range on the surface to be measured, and having a wider dynamic range of measurement than with interferometry. Hence, pattern projection is widely used in many fields.